Rheostat.



PATENTED DEC. 13

H. H. CUTLER.

RHEOSTAT.

APPLICATION FILED NOV. 21, 1902.

2T" EBTS-SHEBT l hide/1hr:

PATENTED DEC. 13

H. H. CUTLER.

RHEOSTAT,

APPLICATION FILED NOV.21,1902.

2 SHBETSSHEBT 2.

N0 MODEL.

y W Am UNITED STATES Patented December 13, 1904.

HENRY H. CUTLER, OF MILWAUKEE, WISCONSIN.

RHEOSTAT.

SPECIFICATION forming part of Letters Patent No. 777,246, dated December13, 1904.

Application filed November 21, 1902. Serial No. 132,255. (No model.)

To (LU whom it may concern.-

Be it known that I, HENRY H. CUTLER, a citizen of the United States,residing at Milwaukee, in the county of Milwaukee and State ofWisconsin, have invented a certain new and useful Improvement inRheostats, of which the following is a full,elear, concise, and exactdescription, reference being had to the accompanying drawings, forming apart of this specification.

My invention relates to means for protecting rheostats to prevent injurythereto by the heating effect of an abnormal current through itsresistances.

In rheostats employed for starting motors means is usually provided forcutting out the resistance slowly, and it often happens thatthe'attendant after partially cutting out the resistance will neglect tofully operate the device to cut out all of the resistance. In this casethe remaining sections of the resistance in the main circuit are liableto become abnormally heated, since they are ordinarily not designed tocarry the abnormal working current. This heating may rise to such anextent as to destroy the rheostat and possibly cause destructive fires.Also in rheostats employed for regulating a portion of its resistance isintended to be always included in the circuit. These resistances aretherefore designed to withstand the normal working cur rent for anylength of time, but in case of an abnormally strong current they arelikewise liable to become heated and destroyed.

My invention is therefore designed to thus protect rheostats fromoverheating; and it consists in providing a thermostat in associa tionwith the parts so liable to become heated which is arranged to controlsuch safety devices as may be employed in connection with the particularrheostat or that it may be desired to employ.

My invention is illustrated in the accompanying drawings, in which thesame reference characters indicate like parts throughout the severalviews, and in which- Figure 1 is a front elevation of a rheostatembodying my'invention. Fig. 2 is a side elevation of the same. Fig. 3is a diagram showing how the circuits may be arranged. Fig. 4 is adiagram of still another arrangement, and Fig. 5 is a diagram of adifi'ei'ent rheostat.

The rheostatic device shown in Figs. 1 and 2 is the same as that shownin my Patent No. 702.409, dated June 17, 1902, although it will beunderstood that the invention is applicable to any other type ofrheostat. This device is, moreover. only generally indicated in Figs. 1and 2, since reference may be had to the said patent for a fulldisclosure of the details thereof. It comprises a suitable insulatingbase 2, upon which are located a plurality of interlocking hand-levers 33, &c., which are pivoted at their lower ends upon a rod 4:, supportedat its ends in bearings 5, suitably secured to the face of saidinsulating-base. In the brackets supporting the bearings 5 and beneaththe rod 4. a second rod 6 is located, said levers 3 being provided withdownwardly extending ends 7, which are adapted to strike against the rod6 to serve as stops for the said levers when they are opened. Theselevers carry bridging-contacts 8, which when closed, as shown in Fig. 2,engage the common contact-bar 9 at their lower ends and the individualcontactblocks 10 at their'upper ends. The resistance of the rheostat isdivided into sections 11, the first section being that at the left andis included between the common eontact-bar 9 and the individual contact10 with which the second lever engages. The remaining sections of theresistance are included between the successive individual contacts. Thefirst lever 3 of the series may be provided with laterally-extendingarms 12, which carry carbon contacts 13, adapted to engage like contactsmounted upon the bar 9 and the first contact 10. These levers areprovided with interlocking catches 14: 14:, &c., by means of which it isimpossible to close the levers in any except the desired order that is,beginning with the first one at the left and then the otherssuccessively toward the right, and when the first lever of the series isreleased all of the others are likewise released and fall away from thefront of the plate. The first lover of the series is provided with a pin15,

which is adapted to engage in the notch of the catch 16 of the armature17 of the releasingmagnet 18 when the said lever is closed. Thisarmature is pivoted at its lower end upon the pivot 19, so that when themagnet is deenergized it opens by gravity, and thereby releases the pin15. This armature is also arranged to fall out of the magnetic field ofthe magnet 18, so that it cannot be raised until the lever 3 is closedand strikes the armature 17 and carries it to the position shown in Fig.2. It is then attracted and maintains the lever closed until the currentis cut elf from the magnet.

A motor is indicated at 20, which has its armature-circuit closed bymeans of conductor 21 to the first of the individual contacts 10, andthence when the first lever is closed through the contacts thereof tothe common bar 9, and thence through the sections of the resistance tothe last contact 10, and thence by conductor 22 to the opposite side ofthe circuit. The releasing-magnet 18 is, as shown, connected between thefirst contact 10 by means of a conductor 23, and thence by conductor 24to the shunt field-winding 25 of the motor, and thence to the other sideof the circuit, the releasing-magnet being therefore connected in serieswith the shunt field-winding of the motor. T/Vhen, therefore, thecurrent on the power-circuit fails, the releasing-magnet will bedeenergized and the first lever 3 will be opened, which will permit allof the others to open. This will open the armature-circuit and preventits closure except through the said resistances.

In case the device is employed as a starting resistance, that being thepurpose of the spe cific construction shown in Figs. 1 and 2, and theattendant should for any reason fail to close all of the switches orlevers 3 the last section or sections 11 of the resistance would remainin circuit. The continued flow of current would therefore be at suchremaining sections, and unless some measure was taken to protect themthey would soon be destroyed. For this purpose l employ the thermostat26, which is not shown in Fig. 1 and which, as shown in Fig.

2, is located within the box in the rear of the base-plate 2, containingthe rheostatic resistances. The resistances, which are only showndiagrammatically in Fig. 1, are in practice formed as shown in Fig. 2and are composed of fiat metallic strips 11, suitably connected incircuit and mounted within the casing or box 27. The thermostat 26 isplaced adjacent a section of the resistance, preferably near the lastsection of the series, so that it can be affected by the rise intemperature of the said resistance to close the contacts 28 and 29.These contacts are included in series with the windings of the magnet30, which is adapted when energized to close the contact 31, carried byits armature and the stationary contacts 32 in a shunt of thereleasing-magnet 18, said shunt comprising the conductors 33 and 3&. henthe shunt is thus closed, the releasing-niagnet is deprived ofoperating-current and releases the levers 3.

The thermostat 26, it will be understood, may be of the usual or anydesired pattern and may be arranged in any desired way to control thesafety devices. The thermostat shown in Fig. 2 consists merely of astraight bar formed of different materials having different coefficientsof expansion and carries at its free end the contact 29, which isadapted normally to be free from the contact 28, but when thetemperature rises to be carried into engagement with contact 28.

The diagram of this apparatus is shown more clearly in Fig. 1, in whichthe thermostat 26 is seen to be in series with the extra magnet 30,together with a resistance-coil 35, which may be the shunt field-windingof the motor or an external resistance, as desired. The contact 31 ofthe armature of the extra magnet 30, as is observed, closes when raisedthe shunt composed of the conductors 33 and 3 1 of the releasing-magnet18, which latter may be included across the line with the resistance 25,which may also be a shunt lieldwinding of the motor or other resistance.It is here clearly shown that when the thermostat is operated by theheating of the resistances it closes the circuit of magnet 30, which isactuated to close the shunt of the releasing magnet which releases thelevers 3 and opens the circuit of the motor.

The arrangement of the thermostat may be varied in many ways, onevariation being shown in Fig. 3, in which the releasing-magnet 18 isconnected with a resistance 36 across the line, which resistance may bethe shuntfield of the motor. The thermostat 26 arranged when closed bythe heat of the resistance 11 to directly shunt the magnet 18, andthereby cause its denergization and the release of the levers 3.

The device shown in Figs. 1 and 2 might with slight modilication beemployed for regulating purposes, in which case the last sections ofresistance would probably be in circuit most of the time. In Fig. 5 lhave shown a different form of ordinary regulating-rheostats, in which apivoted arm 4:0 is adapted to sweep over a series of contacts to cutoutthe sections 11 of resistance. This arm may be placed at any point tosecure the desired speed of the motor, at which point it is held by thedog 41, carried by the armature 42 of the retaining magnet 43, said dogengaging the teeth of the ratchet-segment 14, secured to the lever 10.The thermostat 26 is arranged upon the heating of theresistance-sections remaining in the circuit to close the shunt of themagnet 13, and thereby cause it to release the arm 40, which is returnedto normal position by a suitable coiled spring 45, thereby opening thecircuit of the motor.

It is obvious that still other arrangements may be made withoutdeparting from the spirit of the invention, which broadly consists inprotecting a rheostat by means of a thermostat.

Having described my invention, what I claim as new, and desire to secureby Letters Patent, is-

1. The combination with a rheostat, of the movable element thereof, aretaining-magnet for said movable element, means for returning the sameto its initial position, and a thermostat responsive to the heatgenerated by said rheostat for deenergizing said magnet when the heatproduced by the rheostatic resistance exceeds a prearranged temperature.

2. The combination with a rheostat, of the movable element thereof, aretaining-magnet for said movable element, means for returning the sameto its initial position, and a thermostat responsive to the heatgenerated by said rheostat operating to close a shunt-circuit aroundsaid magnet to deprive the same of current when the heat produced by therheostatic resistance exceeds a prearranged temperature.

3. The combination with a rheostat, of the movable element thereof, aretaining-magnet for said movable element, means for returning the sameto its initial position, a thermostat responsive to the heat generatedby said rheostat, and a switch controlled by said thermostat for closinga shunt-circuit around said magnet, when the heat produced by therheostatic resistance exceeds a prearranged temperature.

4. The combination with a rheostat, of a contact-arm therefor, aretaining-magnet for said contact-arm, means for returning the same toits initial position, a thermostat responsive to the heat generated bysaid rheostat, and a switch controlled by said thermostat for closing ashunt-circuit around said magnet and thereby deenergize the same whenthe heat produced by the rheostatic resistance exceeds a prearrangedtemperature.

5. The combination with a rheostat, of a plurality of contact-armstherefor, a retaining-111agnetfor said arms, means for returning them totheir initial positions, a thermostat responsive to the heat generatedby said rheostat, and a switch controlled by said thermostat for closinga shunt-circuit around said magnet and thereby deenergizing the samewhen the heat produced by the rheostatic resistance exceeds aprearranged temperature.

6. he combination With an electric motor, of a rheostat therefor, amovable element for said rheostat, a retaining magnet for said movableelement connected in parallel with the armature of the motor, athermostat responsive to the heat generated by said rheostat fordeenergizing said magnet when the heat produced by the rheostaticresistance exceeds a prearranged temperature.

7. In a rheostat, in combination, a resistance adapted to be included inan electric circuit, means for adjusting said resistance, aretaining-magnet for said means, a switch for controlling ashunt-circuit around said retaining magnet, a magnet for operating saidswitch, and a thermostatic element associated with said resistance andresponsive to changes in the temperature thereof and controlling thecircuit of the last mentioned magnet, whereby when said resistancebecomes heated to a predetermined degree said retainingmagnet will bedeprived of current by the closing of the shunt-circuit around the sameand permit said means to return to the normal position.

8. In a rheostat, in combination, a resistance adapted to be included inan electric circuit, a plurality of arms for adjusting said resistance,a retaining-magnet for said arms, a switch for controlling ashunt-circuit around said magnet, a second magnet for operating saidswitch, and a thermostatic element associated with said resistance andresponsive to the changes in the temperature thereof and controlling thecircuit of the last-mentioned magnet, whereby when said resistancebecomes heated to a predetermined degree said retaining-magnet will bedeprived of current by the closing of the shunt-circuit around the sameand permit said arms to return to their normal position.

- In witness whereof I have hereunto subscribed my name in the presenceof two witnesses.

HENRY H. CUTLER.

Witnesses:

RoB'r. V. MORTIMER, F. R. BACON.

